KR910004569B1 - Method for receiving audio stereo of television and device therefor - Google Patents

Abstract

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Description

Method for receiving audio stereo of television and device therefor

1 is a frequency spectrum graph of a composite baseband audio signal in a television transmission signal;

2 is a block diagram of a receiving apparatus according to the present invention.

* Explanation of symbols for main parts of the drawings

10: voice baseband signal 12: main channel component

14: pilot signal 16: subcarrier stereo subchannel

18: second voice program channel 20: input terminal

22 bandpass filter 24 RF amplifier

26: mixer 28: local oscillator

30: image detector 32, 34, 36, 44, 46: band pass filter

38, 48: detector 40: FM demodulator

42, 50, 58: low pass filter 52: dbx noise reduction circuit

54: Matrix 56: Delay Equalizer

60: volume controller 62, 64: output stage

66: microprocessor 67: lead wire

68: display 70: D / A converter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement of an audio receiving system for television, and more particularly, to a method and apparatus for receiving an audio stereo of a television which can receive and reproduce stereo sound.

Generally, according to the television broadcasting standard, a frequency band of approximately 80 KHz width is allocated for transmission of audio components of television signals in each 6 MHz television channel. In this frequency band, the RF main audio carrier signal is frequency modulated by a voice baseband signal, thereby generating a main audio and audio transmission signal, and the transmitted main audio audio signal is an RF voice. A television receiver converts a carrier signal into a signal having a center frequency of 4.5 MHz, and the converted 4.5 MHz voice carrier is reproduced as a main audio signal by an FM detector.

Meanwhile, the Federal Communication Commission recently approved a standard for stereo broadcasting of television voices, which is intended to permit the use of the Janice broadcasting system and the dbx noise reduction system. As a result, the conventional technology for transmitting stereo voice signals commonly used in radio broadcasting systems is applied.

That is, the basic FCC-approved system for stereo radio broadcasting is presented in US Patent No. 3,257,511, which was invented by R. Adler, et al., In which the left (L) is commonly referred to as main channel modulation. The logarithmic fit (L + R) of the right (R) audio source signal is directly used to frequency modulate the RF carrier signal, and the difference (LR) between the left and right stereo signals is applied to the radiated RF carrier during frequency modulation. It is used to amplitude modulate a 38KHz subcarrier signal in the form of a suppressed carrier along with the two sideband signals. In addition, a pilot carrier signal of 19KHz is transmitted for synchronization of the FM receiver, and the FM receiver extracts the pilot carrier of 19KHz and multiplies it by two times to convert the 38KHz signal to a 38KHz signal amplitude-modulated (LR) difference signal. It is applied to a synchronous detector reproduced from a stereo carrier. At this time, the reproduced (L-R) modulation is properly matrixed together with the (L + R) main channel modulation to reproduce the original left and right stereo signals.

In addition, such a stereo radio broadcasting system usually has an SCA component that allows a broadcaster to supply reserved background music. The SCA component includes a 67KHz subcarrier modulated by a background channel program, and a main RF carrier signal with stereo modulation. It includes a frequency modulated subcarrier used for frequency modulation.

In addition, various systems and devices have been proposed for transmitting stereo sound in addition to the conventional television image transmission. In most cases, these systems use the above-mentioned stereo transmission technology of radio broadcasting. A separate subcarrier frequency is selected for compatibility. Such a conventional system is U.S. Patent No. 4,048,654 to Wagner, which uses a frequency band for modulating the main audio carrier of a television transmission signal with a composite baseband signal separate from that adopted for FM stereo radio broadcasting. The proposed hybrid baseband signal includes a (L + R) main channel component, an amplified modulated suppression carrier 38KHz subcarrier (LR) component, and a 19KHz pilot component. . Further, also by using a sub-carrier to give a signal having a frequency (f _H) that indicates a feature of the video signal transmitted other embodiment examples 38KHz (LR) instead of the channel carrier to reduce the interference from the video component of the television signal.

The other system disclosed in U.S. Patent No. 3,099,707, invented by RB Dome, adopts a conventional stereo radio broadcasting system, but the (LR) channel subcarrier is 1.5f _H and the pilot signal is 2.5f _H. These frequencies are chosen to minimize the effect of the image component of the television signal appearing on the sideband of the reproduced (LR) channel signal.

In addition, another similar system is proposed in US Pat. ) the upper sideband of the channel signal is adapted to amplitude modulation with a subcarrier having a frequency of 2f _H. Also, even, and also presents the use of sub-carriers to the (LR) channel stereo frequency modulated with a center frequency of 2f _H as a technique for stereo TV sound transmission other, and also that the center frequency of the sacrifice 1.5f _H.

As mentioned above, it is desirable to make full use of the available voice rental capacity in the television by transmitting additional information when transmitting stereo audio components on the stock audio carrier of the transmitted television signal, ie a second audio program. The transmission of the SAP signal is expected to selectively operate a television receiver to reproduce a voice signal associated with the transmitted stereo information or a voice signal associated with the transmitted second voice program including the foreign language domain of the television program. Make it possible.

On the other hand, the prior art for providing a second language capability to the television signal transmitted in this way has been published in U.S. Patent No. 4,048,654 of Wagner, which is already mentioned, this patent employs two channels of stereo signals, In particular, the (L + R) primary channel signal is used for the transmission of the first language audio signal and the (LR) stereo channel signal is used for the transmission of the second language audio signal. Feldman's U.S. Patent No. 3,221,098 also describes a single television using four or more different language voice tracks by forming a composite baseband signal comprising four or more different subcarriers amplitude modulated into different language voice signals. A transmission system has been proposed that allows simultaneous broadcasting with a program, where a composite baseband signal is used to frequency modulate the main RF voice carrier.

Further, unlike the second language system as stereo voice transmission and a second there to use a frequency modulated subcarrier baseband signal around the 2f _H to the language transmitted, which is modulated in one of two different frequency pilot signal shown It is intended to be used to indicate that a service is on the air.

However, the above systems and techniques for transmitting other voice signals in relation to standard television transmission have not been applied in the United States for various reasons, such as low practicality or lack of compatibility with the US television transmission standard.

However, only the concept of the Zenith stereo broadcasting system described in U.S. Patent No. 4,405,994 of Ailes et al. Was accepted, which is a second voice program including a voice transmission system that is fully compatible with US television broadcasting standards. In addition to providing a stereo audio transmission is possible.

In the Zenith stereo broadcasting system, the audio information is located in the region of approximately 4.4 to 4.6 MHz on the video carrier on the television channel distribution, and the audio portion takes only 0.20 MHz, which is occupied by the video (luminance and saturation) signal. It is a small band compared to a large range of bandwidth. On the other hand, the mono audio channel was conventionally transmitted as an (L + R) FM signal having a frequency range of 50 to 15,000 Hz. However, in the Zenith system, a pilot signal is added to the horizontal scan frequency f _H (15.743 KHz) to generate stereo signals. Installation of a new stereo receiver on two channels is permitted, which is located between 16.47 and 46.47 KHz around 2f _H from the bottom of the voice allocation. This second channel is the key to receiving stereo speech, which is a (LR) AM signal with the same frequency range as the mono channel, and stereo is achieved when the LR and L + R signals are combined.

In addition, the Zenith system, there is first provided with a three-channel, that is a second audio program ( "SAP") to the program and other Commentary used in combination of two languages, the SAP channel is 65~95KHz around the FM and 5f _H It has an extended frequency range from 50Hz to 12KHz.

The specific channel is one can be inserted in the remaining area of the negative 98.2~106.5KHz, besides various types of speech channel for processing the audio signal thereof on a home TV set mainly 6.5f _H to be used for voice or data Treatment methods are also known.

One such processing technique is provided by a "separate audible carrier receiver," where the audible frequency is separated from the image carrier, and the audible carrier is transmitted without incident phase modulation (ICPM), so nothing is transmitted to the FM detector. It cannot be reached. Thus, the receiver is not affected at all by the buzz associated with the image.

A second well-known receiver for television audio channel processing is called a " split voice receiver ", which has been used in the television era before the introduction of cross-carrier detection. This converts the video and audio portions of the received television signal to a lower frequency and converts the audio components of the composite signal to be processed to provide audio output. In such a split voice receiver, the tuner's ICPM can generate low frequency noise in the voice output.

In addition, both the separated audible carrier receiver technology and the divided voice receiver technology cannot be used in cable television due to the high FM noise in the oscillator used to downconvert the television signal. To overcome this, an expensive oscillator with a separate tuning system It is not economical for use in cable television systems because it is needed.

The third known form of speech channel processing is called "similarly divided speech receiver". In this technique, separation processing of audio and video signals is used, but synchronization detection coupled with a cross-carrier speech detector is also adapted. Such a technique is disclosed in US Pat. No. 4,405,944, where the Nyquist ICPM is eliminated in a PQL by a specially designed IF carrier with a symmetric response centered around the image carrier. However, although this type of receiver is independent of the ICPM, the microphone, the local oscillator phase noise in the tuner, the inverse mixer supplied through the local oscillator's tuner, and the image related to the frequency modulation generated by the AFC / AFT circuit, This is affected by the distortion caused by the interfering harmonics of the horizontal scan frequency, which is within the range of the pilot signal and the (LR) subchannel and SAP signal.

Therefore, there is a need for a receiving method and apparatus for receiving stereo broadcast television voices to avoid such interference, and the method and apparatus should be able to be used for cable television conditions, and also for cable television converters and local oscillating loops. It should not be affected by harmonics of the television horizontal scan frequency, such as phase noise, caused by jitter.

The present invention has been invented in view of the above circumstances, and provides a receiving method and apparatus having the above advantages by using two separate receivers for the (L + R) signal and the pilot, (LR) and SAP signals. The purpose of this is to improve the quality of television stereo audio reception.

The receiving method and apparatus according to the present invention are for receiving and reproducing stereo television voice tombs, and the transmitted television signal has a voice component including a main carrier signal which is frequency-modulated according to a complex modulation function. This function is formed by amplitude-modulating a first subcarrier having a frequency of 2f _H in accordance with a difference between the first component comprising a sum of stereo-related first and second speech signals and the stereo-related speech signal. And a second component including both sideband suppression carriers. Here the frequency f _H is the horizontal scan line frequency related to the horizontal synchronous signal of the transmitted television signal.

The apparatus according to the present invention also comprises an input device for enhancing the first signal in response to the complex modulation function in response to the transmitted television signal. The cross-carrier detection device is further coupled to receive a first signal for detecting a segment corresponding to the first component of the complex modulation function and for generating a first speech output signal comprising a sum of stereo-related speech signals, The independent FM detection means is further coupled to receive a first signal for detecting a portion corresponding to the second component of the complex modulation function and for generating a second audio output signal comprising a difference in stereo signals associated with it, The devices are coupled to receive first and second audio output signals to produce a first channel audio output and a second channel audio output.

On the other hand, the device according to the present invention converts the first signal into a second intermediate frequency and inputs it to the intermediate carrier detector, and converts the second signal into a second intermediate frequency and input to the independent FM detection means and It may further comprise a combined device.

In addition, the complex modulation function may have a third component including a second subcarrier having a 5f _H frequency modulated according to the third voice signal, wherein a separate FM detection device corresponds to the first signal portion corresponding to the third component. Can be used to selectively detect and generate a third audio output signal therefrom.

Wherein at least one of the first and second audio output signals may be delayed to provide equalization therebetween, such a delay such that the first channel audio output and the second channel audio output are in proper phase. Will be done.

Hereinafter, the configuration, operation, and effects of the present invention will be described in detail with reference to the accompanying drawings.

1 is a graph of a multi-channel voice baseband signal 10 approved for use in television broadcast signals, wherein the baseband signal includes a main channel component 12 using an extended band from 50 Hz to 15 KHz. Is modulated into a (L + R) audio channel which is the sum of the left and right channels, and the subcarrier stereo subchannel 16 centered at twice the frequency of the TV horizontal scanning frequency f _H of 15.73 KHz is the difference between the left and right channels. The carrier suppression amplitude modulation is performed by the (LR) audio channel. In a second audio program channels 18 are provided in _H 5f, pilot subcarriers are inserted into the horizontal frequency f _H. The pilot signal 14 is as used in the conventional receiver in order to simplify the recovery of the (LR) sub-carriers by the synchronization of the FM receiver, the pilot signals f _H of the conventional receiver is extracted and the ship (LR ) the difference signal is applied to the synchronous detector is restored from the sub-carrier amplitude modulation to 2f _H. This technique is also used by the intermediate carrier detector to detect the (L + R) signal, and the image information is detected by the voice detector so that the intermediate carrier phase modulation is performed. Such image information is to be interference with the pilot sub-carriers, and etc. of f _H, 2f _H.

In order to solve the above problem, the present invention does not fix phase to an image signal, and a carrier wave with an independent FM detector for receiving a pilot and (LR) and SAP signals to obtain an (L + R) signal. By using a detector, it is possible to solve the above problem, and in this way harmonics of the horizontal scan frequency of the television can be avoided. In addition, the required output of the independent FM detector is higher than that of the intermediate carrier detector, minimizing phase noise due to jitter in the cable television converter and local oscillating loop.

2 is a block diagram of a cable television stereo audio adapter according to the present invention for reproducing a stereo audio transmission signal, the apparatus of the present invention can be used to receive stereo audio from a direct broadcast television signal as well as a cable television system.

The television signal including the complex modulation function described in FIG. 1 is received by the input stage 20 coupled to the bandpass filter 22 and the microprocessor 66. The signal received at the input 20 may include data used by the microprocessor 66 to perform various functions selected by the user, for example, data from the cable television remote controller. For example, the viewer may choose to receive a main stereo signal or other SAP channel, and the microprocessor 66 may output a signal onto the lead 67 to perform the viewer's selection. In addition, the remote control of the volume is performed by the microprocessor 66 accessing the D / A converter 70 to control the volume control circuit 60, wherein the display 68 combined with the microprocessor 66 is a viewer. Allows visual confirmation of the selection made via the remote control.

On the other hand, the bandpass filter 22 is used to separate the video and the multi-channel audio RF signal from any other signal present in the input terminal 20, such as the data signal, wherein the video and multi-channel audio RF signal is a band Passed from the pass filter 22 to the RF amplifier 24, the RF signal amplified in this amplifier 24 is supplied to the mixer 26 coupled with the local oscillator 28 so that the frequency of the amplified RF signal is new. Converted to intermediate frequency. For example, if the output signal from the RF amplifier 24 contains components of 41.25 and 45.75MHZ and the local oscillator 28 is operated at 30.55 MHz, the output signal from the mixer 26 will have frequencies of 15.2 MHz and 10.7 MHz. It will contain ingredients.

The output signal from the mixer 26 is applied to a band pass filter 32 having a center frequency of 15.2 MHz (image carrier) and a band pass filter 34 having a center frequency of 10.7 MHz (voice carrier). The band pass filter 34 is preferably a ceramic filter, but the band pass filter 32 may be a simple LG filter.

In addition, the output of the bandpass filter 32 is supplied to an image detector 30 having an automatic frequency control (AFC) detector and an automatic gain control (AGC) detector, wherein the AFC and AGC signals are supplied to the local oscillator 28 and the RF amplifier. 24, respectively, and the image detector 30 receives the output of the band pass filter 34. The final output from the image detector 30 includes the main channel component 12 of the voice carrier signal having a center frequency of 4.5 MHz (15.2 MHz to 10.7 MHz), wherein the converted 4.5 MHz voice carrier is 4.5. The (L + R) speech signal filtered by the MHz bandpass filter 46 and then processed by the FM detector 48 to be used for frequency modulation of the speech carrier in the television signal transmitter is reproduced.

The output from the FM detector 48 is also input to a delay equalizer 56 which equalizes between the (L + R) and (LR) signals reproduced by a separate and independent FM detector as described below. . The (L + R) signal is delayed for an appropriate time and then input into the conventional matrix 54 through a 15 KHz low pass filter 58 which limits the signal to the voice frequency finally reproduced. The matrix 54 combines the signal with the (L-R) signal to reproduce the right channel audio signal at the output terminal 62 and the left channel audio signal at the output terminal 64.

On the other hand, to recover the pilot and (LR) and SAP signals, the output of the bandpass filter 34 is passed through a second (ceramic) bandpass filter 36 which provides additional filtering for high fidelity speech reproduction. The output of this bandpass filter 36 is applied to a 10.7 MHz FM detector 38 which recovers (LR) and SAP components 16 and 18, respectively, shown in FIG. The signal detected by the detector 38 passes through a demodulator 40 that selectively demodulates the AM (LR) signal and the FM SAP signal to 431.5 KHz (2f _H ) and 78 KHz (5f _H ), respectively. As the demodulator 40, a 50 KHz low pass filter 42 for demodulating the (LR) component or a 78 KHz band pass filter 44 for demodulating the SAP component is used. It is selected by the mode control signal output from the microprocessor 66.

The demodulated output from the demodulator 40 is applied to a 15KHz low pass filter 50 which limits it to the voice frequency band, and is then input to the reference dbx noise reduction circuit 52, followed by a (LR) signal and (L). The + R) signal is applied to the matrix 54 to generate a predetermined left and right audio channel.

As described above, according to the present invention, stereo broadcast television audio can be reproduced without distortion by the pilot signal of the multi-channel audio baseband signal and the image information interfering with the (L-R) subcarrier and the SPA subcarrier components. In other words, according to the present invention, the best (L + R) channel is formed by using a pseudoparallel carrier detector, and the improved (LR) channel and the SAP channel are identical to those used to reproduce the (L + R) component. It is formed by using a separate voice detector instead of an intermediate carrier detector, and by stereo interference with the harmonics of the horizontal horizontal scan frequency and the pilot and the vertical scan frequency sidebands placed in the (LR) subchannels and SAP signals. Distortion of voice or SAP output is prevented. In addition, only the higher frequency components of the separate FM detector are used to minimize phase noise due to jitter, and to recover the (L + R) channel at a lower frequency where phase noise can be severe, using a standard intermediate carrier detector. Therefore, the television stereo audio reception characteristics are remarkably improved.

Claims (18)

A main carrier signal frequency modulated according to a complex modulation function with a first audio component 12 based on a stereo audio signal, and a frequency different from the first audio component 12, based on other related stereo audio signals Tuning a transmission television signal 10 comprising a speech component comprising a second speech component 16 in a range, and converting the speech component of the television signal to a first speech carrier centered around a first intermediate frequency; Generating a second speech carrier centered on a second intermediate frequency, detecting the first speech component 12 of the complex modulation function from the first speech carrier at a first intermediate frequency, and generating a second speech carrier at a second intermediate frequency Detecting the second speech component 16 of the complex modulation function from the two speech carriers; and the left channel speech output and the right channel speech from the detected first and second speech components 12,16. Stereo audio of a television receiving method including the step of generating a force, it characterized in that it is to receive and play back stereo audio in a television signal. The method of claim 1, further comprising delaying at least one of the detected first and second voice components 12, 16 before the left and right channel voice output generation step. A stereo stereo reception method for television, characterized by providing an appropriate phase relationship between audio components (12, 16). 3. A third speech component (18) according to claim 2, wherein said third speech component (18) of said complex modulation function comprises a second subcarrier having a frequency several times the horizontal scan frequency of said transmission television signal modulated in accordance with a third speech signal. Selectively detecting from an audio carrier and generating a second audio program output from the detected third audio component (18). 2. The first speech component (12) of claim 1, wherein the first speech component (12) comprises a sum of stereo-related first and second speech signals, and the second speech component (16) is stereo-related first. and the second time have a difference between the audio signal is configured by the sub-carrier comprises a double sideband suppressed carrier signal formed by modulating the amplitude, to the sub-carrier is a jupyeong scan line frequency f _H LA related to the horizontal synchronizing signal of the transmitted television signal, 2f An audio stereo reception method for television, characterized by having a frequency of _H. A detection circuit for detecting the first and second audio components 12 and 16 associated with the television signal, and a left channel audio output and a right channel audio output from the detected first and second audio components 12 and 16; And a stereo audio output from the television signal 10 having the first and second audio components 10 and 12 associated therewith and separated as a left channel audio output and a right channel audio output. In an audio stereo receiver of a television, which is capable of outputting, the detection circuit further comprises a first detector (48) for detecting the first audio component (12) and a separate for detecting the second audio component (16). An audio stereo receiver of a television, comprising: a second detector (38). The method of claim 5, wherein the first audio component 12 is converted into a first intermediate frequency for input into the first detector 48, and the second audio component 16 is converted into the second detector 38. And a conversion circuit (26, 28) for converting to a second intermediate frequency for inputting into a digital audio receiver. 7. The method of claim 6, wherein the first audio component 12 is the sum (L + R) of the left and right stereo channels, and the second audio component 16 is the difference (LR) between the left and right stereo channels. An audio stereo receiver of a TV, characterized in that. 8. An audio stereo receiver according to claim 7, characterized in that said second detector (38) is an FM detector. 8. The television signal according to claim 7, wherein the television signal (10) has a main carrier signal that is frequency-modulated according to a complex modulation function comprising the associated first and second audio components (12, 16). 16 is a stereo audio of a television receiving apparatus, characterized in that the modulation of the first sub-carrier having a frequency of 2f _H to the horizontal scanning line frequency related to the horizontal synchronizing signal of the television signal (10) f _H (d) 10. A television audio stereo receiver according to claim 9, wherein said first detector is an intermediate carrier detector. 11. The apparatus of claim 10, wherein the second detector (38) is an FM detector. 12. The apparatus of claim 11, further comprising a third speech component (18) comprising a second subcarrier having a frequency several times the frequency (f _H ) modulated according to the third speech signal. The FM detector 38 comprises means for selectively detecting said main carrier signal portion corresponding to said third speech component 18, so as to generate said third speech output signal. TV's audio stereo receiver. 6. The apparatus of claim 5, further comprising a delay circuit (56) for equalizing the phases of the left channel audio output and the right channel audio output. A tuner for receiving the transmission television signal 10, frequency converting circuits 26, 28 coupled to the tuner for converting the audio portion of the received television signal to an intermediate frequency, and the frequency converting circuits 26, 28; A detection circuit for detecting the first and second audio components 12 and 16 of the television signal 10 after conversion by means of receiving and receiving television stereo audio from the associated first and second audio components 12 and 16; In an audio stereo receiver of a television which is capable of being reproduced and outputted separately to a left channel and a right channel audio output, the frequency conversion circuits 26 and 28 have the first audio component 12 centered on a first intermediate frequency. Converts a second speech component 16 into a second speech carrier centered on a second intermediate frequency, and the detection circuit converts the first speech component 12 at a first intermediate frequency. Article to detect) And a second detector (38) for detecting the second audio component (12) at a second intermediate frequency. 15. The apparatus of claim 14, wherein the first detector (48) is an intermediate carrier detector. 15. The apparatus of claim 14, wherein the second detector (38) is an FM detector. 17. The apparatus of claim 16, wherein the first intermediate frequency is 4.5 MHz and the second intermediate frequency is 10.7 MHz. 15. The television signal (10) according to claim 14, wherein said television signal (10) is provided with a third audio component (18) for modulating a main carrier having a frequency several times the horizontal scan line frequency of said television signal (10). And a switchable demodulator (66, 67, 40, 42) to enable selective demodulation of the third audio component (16, 18).

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